Antenna system having a reflector with a substantially open construction

ABSTRACT

Disclosed is an antenna system having a reflector with an open construction and improved suppression of radiation leakage through the reflector. One embodiment of the invention includes a planar grid of parallel conductive columns having linearly polarized antenna elements mounted on the columns, with the polarization of the elements parallel to the columns. Colinear arrays of tuned reflective elements are interspersed with the columns to cause suppression of radiation leakage through the grid of conductive columns. The planar grid and colinear arrays collectively form a reflector which is open to passage of wind but closed to passage of electromagnetic wave energy.

United States Patent [19] Wheeler Sept. 17, 1974 ANTENNA SYSTEM HAVING A REFLECTOR WITH A SUBSTANTIALLY OPEN CONSTRUCTION I [75] Inventor: Harold A. Wheeler, Smithtown,

[73] Assignee: Hazeltine Corporation, Greenlawn,

[22] Filed: June 25, 1973 [21] Appl. No.: 373,203

[52] US. Cl. 343/815, 343/912 [51] Int. Cl. H0lq 21/12 [58] Field ofSearch 343/834-838, 343/846, 817,818, 815, 912

[56] References Cited UNITED STATES PATENTS 2,115,789 5/1938 Schmid 343/818 2,210,666 8/1940 l-Ierzog 2,213,859 9/1940 Hahnemann 343/836 2,558,727 7/1951 Bernet 343/815 FOREIGN PATENTS OR APPLICATIONS 704,953 3/1931 France 343/818 Primary ExaminerEli Lieberman [5 7] ABSTRACT Disclosed is an antenna system having a reflector with an open construction and improved suppression of radiation leakage through the reflector. One embodiment of the invention includes a planar grid of parallel conductive columns having linearly polarized antenna elements mounted on the columns, with the polarization. of the elements parallel to the columns. Colinear arrays of tuned reflective elements are interspersed with the columns to cause suppression of radiation leakage through the grid of conductive columns. The planar grid and colinear arrays collectively form a reflector which is open to passage of wind but closed to passage of electromagnetic wave energy.

13 Claims, 6 Drawing Figures FIG. 3c

l9 PRIOR ART FAI ENIED SEN mu FlG.3b

1 1 1' (Xe (2Q I I FIG. I

FIG. 30

ANTENNA SYSTEM HAVING A REFLECTOR WITH A SUBSTANTIALLY OPEN CONSTRUCTION BACKGROUND OF THE INVENTION larization of the element substantially parallel to the columns. The antenna system additionally includes a plurality of colinear arrays of selectively tuned reflective elements, the arrays being substantially parallel to the columns and selectively interspersed with the columns, the tuning of said elements and the location of said arrays with respect to the columns being selected to cause suppression of leakage of the radiated wave energy through the grid of conductive columns. Finally the antenna system includes means for supporting the antenna elements, the columns and the arrays.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in con- In some systems the antenna requires a reflector of junction with the accompanying drawings and its scope a substantial physical size in which case the use of a solid conductive surface as a reflector causes the reflector to be subjected to substantial wind forces. The wind forces on the antenna require the use of extensive mechanical structure to maintain the reflector surface in the desired contour and prevent damage to the reflector. In addition, wind loading makes it more difficult to rotate a mechanically steered antenna, necessitating the use of a large motor for rotation.

In order to reduce wind loading on the reflector, previous designs have used a reflector comprising a grid of parallel conductive columns. This reflector type has a low wind loading, but a substantial portion of the incident radiation leaks" through the grid. The reflector leakage is not a significant problem when the reflector is a curved focusing reflector, but in the case of a planar array, radiation which leaks through the reflector forms a focused back lobe which is highly undesirable.

In a paper entitled The Radiation Resistance Of An Antenna In An Infinite Array Or Waveguide, published in the Proceedings of The Institute of Radio Engineers, Vol. 36, No. 4, April I948, the present inventor, Harold A. Wheeler, indicated that a reflective surface can be formed from an array of reflective elements comprising half-wavelength elongated conductors, and an antenna of this type is shown by R. C. Hanson in Microwave Scanning Antennas," Volume II, Academic Press, New York, 1966, page 366. Such an array of reflective elements, however, cannot be used to support antenna elements since transmission lines which conduct wave energy to the elements would detune the array.

SUMMARY OF THE INVENTION It is an object of this invention, therefore, to provide a new and improved antenna system having a reflector with a substantially open construction.

It is a further object of this invention to provide such an antenna system having a reduced amount of radiation leakage through the reflector.

It is a still further object of this invention to provide such an antenna system having conductive columns in the reflector upon which antenna elements may be mounted.

In accordance with the invention, there is provided an antenna system having a reflector with an open construction and improved suppression of radiation leakage through the reflector. The antenna system includes a reflective grid of substantially parallel conductive columns and at least one linearly polarized antenna element for radiating wave energy, arranged with the powill be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an antenna system constructed in accordance with the present invention.

FIG. 2 indicates one suitable technique for mounting an antenna element onto a conductive column.

FIGS. 3a, 3b and 3c illustrates a colinear array of reflective elements.

FIG. 4 is a top view of the FIG. 1 antenna system illustrating its operation.

DESCRIPTION AND OPERATION OF THE FIG. I ANTENNA SYSTEM The antenna system of FIG. 1 includes a plurality of dipoles 10, which are antenna elements for radiating wave energy. The dipoles 10 are mounted on conductive columnsll, which form a planar grid. Interspersed with the conductive columns 11 are colinear arrays 12 of reflective elements 13. The colinear arrays 12 and conductive columns 11 are held in position by supporting structure 14. The planar grid of conductive columns and colinear arrays has an open construction; that is, the spacing between columns and arrays is greater than the cross section of the arrays and columns, preferably much greater.

The conductive columns 11, colinear arrays I2 and supporting structure I4 form a planar-shaped reflector for wave energy. All of the dipoles 10 are mounted on the conductive columns 11, facing one side of this planar reflector. The reflector has a size and shape similar to the size and shape of a conventional solid metallic reflector for a planar array of dipole elements. The location and number of dipoles 10 are chosen in accordance with principles familiar to those skilled in the antenna art, as are the amplitude and phase of wave energy signals supplied to each of the dipoles 10. The dipoles 10 in the FIG. I antenna are arranged so that the polarization of the elements is parallel to the conductive columns 11.

Linearly polarized elements other than dipoles may be used in antenna systems which embody the present invention, as long as the elements are arranged to have a polarization which is parallel to the conductive columns 11. An example of another element type which might be used is a resonant loop antenna.

FIG. 2 illustrates one technique for mounting a typical dipole element 10 onto a conductive column 11. In this embodiment the conductive column 11 is hollow so that the transmission line 15, which supplies wave energy to the dipole 10, may pass through the conductive column 11. In this way, the presence of the transmission line 15 has no effect on the radiation properties of the antenna system. It will be evident to those skilled in the art that the transmission line I5 may also be located outside the conductive column 11 and present substantially no interference to the radiation properties of the antenna so long as the transmission line 15 is in close proximity to the conductive column 11 and is grounded to the conductive column 11.

FIG. 3 illustrate a portion of one of the colinear arrays 12 of reflective elements I3. In the embodiment of FIG. 3 the colinear array I2 is formed by using a nonconducting core 16 of insulating material. Mounted to the outside of the core I6 are reflective elements 13, which comprise elongated conductive cylinders. The length, diameter and spacing of the reflective elements I3 are chosen so that the reflective elements 13 will be tuned to cause the suppression of radiation through the grid of conductive columns 11 in the FIG. 1 antenna.

The reflective elements 13 need not be cylindrical in shape but may have another shape which is more convenient to the particular embodimet. In some applications the reflective elements 13 might be elongated strips of conductive material formed on a flat nonconducting surface.

The tuning of the reflective elements I3 is the significant feature of the present invention. It is well known in the art that an elongated conductor, which is effectively a half wavelength long at the operating frequency, is self-resonant; that is, the currents in the halfwavelength conductor in the presence of an electromagnetic field will be substantially greater than in a continuous conductor. In the case of a half-wavelength reflective element, the natural inductance of the conductor is tuned out by its own self-capacitance to result in resonance wherein the reflective element has a minimum amount of impedance.

When placed in an electromagnetic field of wave energy of the proper frequency, the half-wavelength element carries a maximum amount of current.v This current results in secondary radiation which may interfere with the incident electromagnetic field in certain directions. Because of the higher amount of current associated with a resonantly-tuned reflective element, the interference with the incident wave energy is greater than with a nonresonant element. It is, therefore, evident that the amount of interference of a reflective element with an incident wave energy field may be adjusted by selectively tuning or detuning ofthe reflective element, that is, by adjusting its length. The amount of secondary radiation of a reflective element changes slowly with frequency, hence the interference effect will be present over a finite frequency band.

The colinear array of reflecting elements 13, shown in FIG. 3a, consists of conductive elements 13, which are less than a half wavelength in length. These elements may also be tuned to be resonant by suitable adjustment of the spacing between adjacent elements in the colinear array. This spacing provides a capacitance which can be used to tune the inductance of the shortened elements 13. The amount of secondary radiation from the colinear array of FIG. can be similarly adjusted as the secondary radiation of the isolated half wavelength resonant reflecting element. The FIG. 3a colinear array has more desirable properties than a colinear array of half-wavelength elements since it has inherently a broader bandwidth of resonance. Bandwidth may also be increased by increasing the diameter of the reflective elements, but this has the effect of increasing wind resistance.

Alternates to the FIG. 3a colinear array are shown in FIG. 3b and BC. In the FIG. 3b array the capacitance required for tuning the inductance of the reflective elements 13 is provided by fixed capacitors 17. The FIG. 30 array is similar in design to the FIG. 3a array but additionally includes a protective cover 18 of dielectric material to prevent deterioration of the array tuning by a coating of precipitation on the colinear array.

The operation of the FIG. 1 antenna system may be easily explained after having considered the properties of the colinear arrays 12. In the absence of the colinear arrays 12, linearly polarized Wave energy radiated by the dipoles It) would be partially reflected and partially transmitted through the grid of conductive columns II. The colinear arrays 12 are selectively tuned so that the secondary radiation from the elements 13 of the colinear arrays 12 will be equal in amplitude to the wave en ergy passing through the grid of conductive columns II. The location of the colinear arrays 12 selectively is adjusted so that the phase of the secondary radiation from the reflective elements 13 will be opposite to the phase of the wave energy passing through the grid of conductive columns II. In most instances the colinear arrays 12 will be approximately co-planar with the conductive columns 11. The secondary radiation from the colinear arrays 13, interferes with the wave energy passing through the grid of conductive columns 11 and causes a substantial reduction in the leakage of wave energy signals through the reflector. The colinear arrays 12 may be thus adjusted in amplitude and phase to cause perfect cancellation of the wave energy leakage in a particular direction or a substantial cancellation over a particular range of angular directions.

It is usually desired that the dipoles 10 of the FIG. 1 antenna radiate a single antenna beam. Since in the FIG. 1 embodiment the dipole spacing is equal to the spacing of the conductive columns 11, this spacing will usually be chosen to be less than one wavelength at the operating frequency to avoid the presence of undesired extra antenna beams called grating lobes." A spacing of less than one wavelength will usually allow substantial cancellation of leakage radiation by placing a single column of reflective elements in each space between adjacent conductive columns in the grid. In this case, the reflective elements are most effective if they are arranged to be equidistant from the nearest pair of conductive columns.

A reflector having the structure shown in FIG. 1 is most desirabe in the case where the antenna is in the form of a planar array of elements. As illustrated in FIG. 4, without the use of the present invention, the array of elements 10, when supplied with wave energy signals of equal phase, will have a main desired antenna beam 22 which is perpendicular to the plane of the grid 21 of conductive columns 11. Leakage of wave energy through the grid 21 of conductive columns 11 will also cause an antenna beam 19, called a back lobe, in the direction opposite to the desired antenna beam 22. The wave energy signal passing through the grid 21 of conductive columns will be substantially in focused phase and the undesired beam 19 will have a substantial amplitude with respect to the desired beam 22. When the colinear arrays 12 of reflective elements 13 are interspersed with the grid 21 of conductive columns 11, the

result is a substantial reduction in the amount of radiation leakage through the grid 21 of conductive columns 11. The undesired beam 19 will be substantially reduced in magnitude because of the reduction of radiation leakage through the grid 21 of conductive columns 11 and a beam will be formed which has an acceptable low amplitude with respect to the main beam 22.

The use oftuned" colinear arrays-in the present invention is significantly more effective in reducing the back lobe radiation than the use of corresponding conductive columns in place of the arrays. Experiments have indicated that the back lobe radiation for an antenna with conductive columns in place of the colinear arrays is only 13 dB below the amplitude of the desired antenna beam 22. For the same configuration, using the tuned colinear arrays, the back lobe radiation was suppressed to 35 (18 below the amplitude of the desired antenna beam 22.

in this experiment the ground plane comprised conductive columns 0.20 wavelengths in diameter, spaced 0.88 wavelengths apart at the operating frequency. The reflective elements were conductive cylinders 0.05 wavelengths in diameter and 0.26 wavelengths long. The reflective elements were tuned by adjusting the gap between elements which was approximately 0.01 wavelengths. A single linearly polarized antenna element was used which was placed 0.20 wavelengths from one of the conductive columns.

The present invention is advantageously applied to the planar array of radiating elements, as shown in FIG. 1. It will be evident to those skilled in the art. however, that the invention may be used to form reflectors of substantially open construction for use in other antenna systems. One such alternate embodiment would comprise a focusing reflector with a substantially open construction and a linearly polarized antenna element for illuminating the reflector with wave energy. Another alternate embodiment would comprise a nonplanar array of antenna elements having a non-planar reflecting surface constructed in accordance with the present invention.

These alternate embodiments do not have the critical need for a low amount of radiation leakage that is present in the planar array wherein the radiation leakage through the reflector forms a focused back lobe, but will have the advantage of higher gain than reflectors with a substantially open construction which are built in accordance with prior art.

in describing the various embodiments above, reference has been made to transmitting antenna systems, but it will be recognized by those skilled in the art that the principles of the present invention can also be applied to receiving antenna systems. Accordingly, the appended claims shall be construed as covering both transmitting and receiving antenna systems regardless of the descriptive terms actually used therein.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is therefore aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

a reflective grid of substantially parallel conductive columns;

at least one linearly polarized antenna element for radiating wave energy, arranged with the polarization of said element substantially parallel to said columns;

a plurality of colinear arrays of selectively tuned reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the tuning of said elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns;

and means for supporting said antenna element, said columns and said arrays.

2. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

a reflective grid of substantially parallel conductive columns;

a plurality of linearly polarized antenna elements for radiating wave energy, said antenna elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns;

a plurality of colinear arrays of selectively tuned conductive reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns;

and means for supporting said columns and said arrays.

3. An antenna system as specified in claim 2 wherein said grid of conductive columns is a planar grid.

4. An antenna system as specified in claim 3 wherein said parallel conductive columns are equally spaced in said planar grid.

5. An antenna system as specified in claim 2 wherein said antenna elements are dipoles.

6. An antenna system as specified in claim 2 which additionally includes transmission lines for supplying energy to said antenna elements, said transmission lines being located within the conductive columns supporting the corresponding antenna elements.

7. An antenna system as specified in claim 2 wherein there is one of said arrays located in every space between adjacent conductive columns in said grid.

8. An antenna system as specified in claim 8'wherein each of said arrays is equidistant from said adjacent conductive columns.

9. An antenna system as specified in claim 2 wherein each of said arrays comprises a column of insulating material having a plurality of conductive reflective elements mounted thereon.

10. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

a planar grid of substantially parallel, equally spaced conductive columns;

flective elements, comprising columns of insulating material having a plurality of conductive reflective elements mounted thereon, said arrays being paral tion leakage through said reflector, comprising:

reflective grid of substantially parallel conductive columns;

a plurality of linearly polarized antenna elements for lel to said conductive columns and selectively indi ti ve e rgy, aid elements being tersllersed with Said Conductive Columns, one f mounted on at least some of said columns with the Said arrays being located in Space between polarization of said elements substantially parallel adjacent conductive columns and each of said arto i columns;

rays beihg equidistant from the nearest P of said a plurality of co-linear arrays of selectively tuned columns; 10 conductive reflective elements, each of said refleca plurality of diPOIB elemehts for radiating tive elements being effectively near l/2-wavelength wave energy signals, said dipoles bemg mounted 0 invlength at the operating frequency of said antenna said columnswlth the polarization of said dipoles system and Said arrays being Substantially parallel Parallel to sand columns; to said columns and selectively interspersed with and means for Suppomng columns and Sand said columns, the length of said conductive elerays; ments and the location of said arrays with respect whereby when wave. energy i radiated by Said to said columns being selected to cause suppression tenna elements, said reflective elements cause supof leakage of said radiated wave. energy through pression of radiation leakage through said grid of Said grid of conductive columns; conducnve columns and means for supporting said columns and said arll. An antenna system having a reflector with an ra 5 open construction and improved suppressiim of radia' l3. antenna system having a reflector with an leakage hrough said reflector compnsmgz open construction and improved suppression of radiaa planar gm of substamlaily equally Spaced tion leakage through said reflector, comprising:

3g: :333 3: 2:3 5 ifiggi ggff s ifizg a zzflltelitrige grid of substantially parallel conductive antenna s stem;

.a plurality 0 f linearly polarized antenna elements, for a plurality of nearly polarized antenna elements f radiating wave energy, said antenna elements being rad'atmg wave energy @lemems bemg mounted on at least some of said columns with the f l at some 0 Sald columns the polarization of said elements substantially parallel polarllzanon of 531d elements substantially Parallel to said columns; to clumns I a plurality of co-linear arrays of selectively tuned a plurahtlf of h arrays of selechvely tuned conductive reflective elements, said arrays being ciohduchve reflechve elements each of Said substantially parallel to said columns and selecelements being less than l/2'wavfilength tively interspersed with said columns, the length of length at the Operahhg frequency of said antenna said conductive elements and the location of said System, and Said arrays being Substantially Parallel arrays with respect to said columns being selected to Said Columns and Selectively interspersed with to cause suppression of leakage of said radiated Said Columns, the length of Said conductive wave energy through said grid of conductive col- 40 ments, the spacing between adjacent elements in umns; said co-linear arrays, and the location of said arrays and means for supporting said columns and said arwith respect to said columns being selected to rays. cause suppression of leakage of said radiated wave 12. An antenna system having a reflector with an energy through said grid of conductive columns. open construction and improved suppression of radia- Page 1 of UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,836,977 Dated September 17, 1974 Inventor) Harold A. Wheeler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claims 1 13 should appear as shown below:

. 1. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

. a reflective grid of substantially parallel conductive columns;

at least one linearly polarized antenna element for radiating wave energy, arranged with the polarization of said element substantially parallel to said columns;

a plurality of colinear arrays of selectively tuned reflective elements said arrays being substantially parallel to said columns and selectively interspersed with said columns, the tuning of said elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns;

' P UNITED STATES PATENT OFFICE age 2 of 7 CERTIFICATE OF CORRECTION Patent 3,836 ,977 Dated September 17 1974 Harold A. Wheeler Inventor(s) It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

and means for supporting said antenna element,

said columns and said arrays.

2. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

a reflective grid of substantially paralled conductive columns;

a plurality of linearly polarized antenna elements for radiating wave energy, said antenna elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns;

a plurality of colinear arrays of selectively tuned conductive reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements and the location of said arrays with respect to said UNITED STATES PATENT OFFICE Page 3 of 7 CERTIFICATE OF CORRECTION Patent No. 3,836,977 Dated September 17, 1974 Inventor) Harold A. Wheeler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

. columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns;

. and means for supporting said columns and said arrays,

3. An antenna system as specified in claim 2 wherein said grid of conductive columns is a planar grid.

4. An antenna system as specified in claim 3 wherein said paralled conductive columns are equally spaced in said 0 planar grid.

5. An antenna system as specified in claim 4 wherein said spacing between adjacent columns is less than one wavelength at the operating frequency of the antenna system. I

6. An antenna system as specified in claim 2 wherein said antenna elements are dipoles.

Page 4 of 7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 a 836 7 Dated September 17 1974 Harold A. Wheeler Inventor(s) It is certified -that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

7. An antenna system as specified in claim 2 which additionally includes transmission lines for supplying energy to said antenna elements, said transmission lines being located within the conductive columns supporting the corresponding antenna elements.

8. An antenna system as specified in claim 2 wherein there is one of said arrays located in every space between adjacent conductive columns in said grid.

9. An antenna system as specified in claim 8 wherein each of said arrays is equidistant from said adjacent conductive columns.

10. An antenna system as specified in claim 2 wherein each of said reflective elements is a conductive element,

effectively near one-half wavelength in length at the operating frequency of said antenna system.

P 5 UNITED STATES PATENT OFFICE age of 7 CERTIFICATE OF CORRECTION Patent No. 3 ,836 ,977 Dated September 17, 1974 Harold A. Wheeler Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

11. An antenna system as specified in claim 2 wherein said reflective elements are conductive elements less than one-half wavelength in length at the operating frequency of said antenna system and are selectively tuned by adjusting the spacing between adjacent elements in said colinear array.

12 An antenna system as specified in claim 2 wherein each of said arrays comprises a column of insulating material having a plurality of conductive reflective elements mounted thereon.

13. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising:

a planar grid of substantially parallel,

equally spaced conductive columns;

Page 6 of 7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa 3,836 ,977 Dated September 17, 1974 Harold A. Wheeler Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

a plurality of colinear arrays of selectively tuned reflective elements, comprising columns of insulating material having a plurality of conductive reflective elements mounted thereon, said arrays being parallel to said conductive columns and selectively interspersed with said conductive columns, one of said arrays being located in every space between adjacent conductive columns and each of said arrays being equidistant from the nearest pair of said columns;

a plurality of dipole antenna elements for radiating wave energy signals, said dipoles being mounted on said columns with the polarization of said dipoles parallel to said columns;

and means for supporting said columns and said arrays;

whereby when Wave energy is radiated by said Page 7 of 7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,836,977 Dated September 1974 Inventoflg) Harold A. Wheeler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

antenna elements, said reflective elements cause suppression of radiation leakage through said grid of conductive columns. D

Signed and Emalcd this Mel/m Day of July/977 O [SEAL] Attest:

RUTH c. MASON c. MARSHALL DANN Allesti g Off Commissioner of Patents and Trademarks 

1. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a reflective grid of substantially parallel conductive columns; at least one linearly polarized antenna element for radiating wave energy, arranged with the polarization of said element substantially parallel to said columns; a plurality of colinear arrays of selectively tuned reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the tuning of said elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns; and means for supporting said antenna element, said columns and said arrays.
 2. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a reflective grid of substantially parallel conductive columns; a plurality of linearly polarized antenna elements for radiating wave energy, said antenna elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns; a plurality of colinear arrays of selectively tuned conductive reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns; and means for supporting said columns and said arrays.
 3. AN antenna system as specified in claim 2 wherein said grid of conductive columns is a planar grid.
 4. An antenna system as specified in claim 3 wherein said parallel conductive columns are equally spaced in said planar grid.
 5. An antenna system as specified in claim 2 wherein said antenna elements are dipoles.
 6. An antenna system as specified in claim 2 which additionally includes transmission lines for supplying energy to said antenna elements, said transmission lines being located within the conductive columns supporting the corresponding antenna elements.
 7. An antenna system as specified in claim 2 wherein there is one of said arrays located in every space between adjacent conductive columns in said grid.
 8. An antenna system as specified in claim 8 wherein each of said arrays is equidistant from said adjacent conductive columns.
 9. An antenna system as specified in claim 2 wherein each of said arrays comprises a column of insulating material having a plurality of conductive reflective elements mounted thereon.
 10. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a planar grid of substantially parallel, equally spaced conductive columns; a plurality of colinear arrays of selectively tuned reflective elements, comprising columns of insulating material having a plurality of conductive reflective elements mounted thereon, said arrays being parallel to said conductive columns and selectively interspersed with said conductive columns, one of said arrays being located in every space between adjacent conductive columns and each of said arrays being equidistant from the nearest pair of said columns; a plurality of dipole antenna elements for radiating wave energy signals, said dipoles being mounted on said columns with the polarization of said dipoles parallel to said columns; and means for supporting said columns and said arrays; whereby when wave energy is radiated by said antenna elements, said reflective elements cause suppression of radiation leakage through said grid of conductive columns.
 11. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a planar grid of substantially parallel, equally spaced conductive columns, said spacing being less than one wavelength at the operating frequency of the antenna system; a plurality of linearly polarized antenna elements, for radiating wave energy, said antenna elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns; a plurality of co-linear arrays of selectively tuned conductive reflective elements, said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns; and means for supporting said columns and said arrays.
 12. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a reflective grid of substantially parallel conductive columns; a plurality of linearly polarized antenna elements for radiating wave energy, said elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns; a plurality of co-linear arrays of selectively tuned conductive reflective elements, each of said reflective elements being effectively near 1/2-wavelength in length at the operating frequency of said antenna system, and said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements and the location of said arrays with resPect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns; and means for supporting said columns and said arrays.
 13. An antenna system having a reflector with an open construction and improved suppression of radiation leakage through said reflector, comprising: a reflective grid of substantially parallel conductive columns; a plurality of linearly polarized antenna elements for radiating wave energy, said elements being mounted on at least some of said columns with the polarization of said elements substantially parallel to said columns; a plurality of co-linear arrays of selectively tuned conductive reflective elements, each of said reflective elements being less than 1/2-wavelength in length at the operating frequency of said antenna system, and said arrays being substantially parallel to said columns and selectively interspersed with said columns, the length of said conductive elements, the spacing between adjacent elements in said co-linear arrays, and the location of said arrays with respect to said columns being selected to cause suppression of leakage of said radiated wave energy through said grid of conductive columns. 